Modern autorack cars, which is to say autorack cars built since about 1975, have typically had the structure of a flat car underframe covered by a surface defining a main deck for supporting automotive vehicles. Most typically an upstanding elevated-deck supporting framework is mounted to the underframe. Since about 1975 the framework has usually been enclosed within, or used also to support, a large, rather barn-like housing with end doors, the better to discourage thieves and vandals. This superstructure is typically referred to collectively as the “rack” or “racks” of the autorack. Most typically the framework structure includes a series of vertical posts spaced along the sides of the car, and one or two additional decks spaced upwardly from the main deck upon which respective second and third layers of automotive vehicles may be transported. That is, the rack may be a bi-level rack (i.e., a single elevated deck spaced upwardly above the main deck of the underframe) or a tri-level rack (two upper decks rather than one). The framework typically includes an array of sideposts spaced along the car, with diagonal bracing or shear web panels between the posts, as may be. The cars tend to be as tall as permitted under AAR Plate ‘J’, namely 19′-0″ or plate ‘K’, namely 20′-2″ maximum height above Top of Rail. This housing may tend to have gable ends and bridge plates that are moved to an extended position to span the gap between cars during loading and unloading. Those ends, when open to permit circus loading of the cars, i.e., sequential loading of the automotive vehicles by driving in one end, and out the other on arrival. Although other kinds of doors are known, most typically radial arm doors are mounted at the gable ends and are movable between open and closed positions to govern loading and unloading of the cars. The racks are typically replaced twice during the economic life of the autroack car underframe. That is, the old rack is removed from the underframe and replaced with a new set of racks.
Autorack cars are usually found in either a bi-level configuration (i.e., the main deck, plus a single upper deck suspended above the main deck) or in a tri-level configuration (i.e., the main deck and two decks suspended one above the other upwardly of the main deck).